1. Field of the Invention
The present invention relates to a vitamin C bio-sensor, and in particular relates to a separative extended gate field effect transistor based vitamin C sensor.
2. Description of the Related Art
Vitamin C is an antioxidant related to oxidation of aromatic amino acids, and synthesis of norepinephrine. Vitamin C also plays a role of reducing the Fe3+ ions when transferring ferritin in bodily fluids. Vitamin C is needed for hydrogenation of lysine and proline and is mainly in collage. Collagen is needed for growth of cartilage and bone. Lack of vitamin C, leads to hemorrhaging.
The ion sensitive field effect transistor (ISFET) was first invented by P. Bergveld in 1970, and the ISFET is based on a metal-oxide-semiconductor field effect transistor (MOSFET). Moreover, the gate of the MOSFET was replaced by a sensing membrane and electrolyte. A sensing membrane and H+ and OH− in a sample solution results in an adsorption-binding effect to make the potential on the surface of an electrode change, thus obtaining the ion concentration of a sample solution.
If an appropriate enzyme is selected to be on the ion sensing film, concentration of different enzymes may be detected. This structure is called an enzyme field effect transistor (EnFET). The earliest report of EnFETs, used EnFETs for detecting penicillin. After that, various enzyme field effect transistor based structures were used as enzyme bio sensors.
In 1995, R. Nagata and I. Karube et al used a screen printing process to fabricate an amperometric glucose sensor. A plastic film was used as a substrate, and platinum was used as electrodes. Glucose oxidase coated with ferrocence, n-pentanol and polyvinylutyral were mixed as an ink. The ink was sprayed on the platinum electrodes and the ferrocence was used as an electron mediator to decrease the oxidation reduction potential to resist interferon of other ions. Resin was used as physical colloid immobilized substance. After the ink was dried, the ion sensing film was immobilized on the platinum electrodes.